The present invention relates in general to semiconductor device packaging and, more particularly, to semiconductor components housed in packages having improved heat transfer characteristics.
There is a continuing demand for electronic systems with a higher functionality and smaller physical size. With this demand, there are several challenges that face electronic component designers and manufacturers. Such challenges include the management of heat generated by power semiconductor devices, which are typically arranged closely together or next to sensitive logic circuits on electronic circuit boards.
In current configurations, plastic encapsulated devices are commonly used. One problem with plastic packages is that the thermal conductivity out of a package is often limited by the plastic molding material. As a result, the majority of the heat generated by the semiconductor device is transferred through the lower part of the package next to the printed circuit board. Because the printed circuit boards are becoming more densely populated, the boards cannot properly dissipate or handle large amounts of heat. When this happens, the boards can warp, which can cause damage to both the board and the components on the board. In addition, the heat itself can damage other components on the printed circuit board or the materials that make up the board.
In view of this problem, the semiconductor industry is migrating to packages that have the capability of transferring heat out through the top of the package instead of through the printed circuit boards. Such packages may also include a heat sink attached to the top of the package to further aid in heat transfer.
One such package is the DirectFET™ package shown in a Board Mounting Application Note AN-1035 entitled “DirectFET™ Technology” dated Jan. 2002 by International Rectifier Corporation. In this design, plastic mold compound is eliminated altogether because of its perceived poor heat transfer characteristics.
This design has several disadvantages. First, because the package does not use mold compound, the semiconductor is left unprotected making it susceptible to damage or contamination. Also, this design utilizes non-standard manufacturing techniques, which adds to manufacturing cycle time and increases manufacturing costs. In addition, in certain applications this design places the main current carrying electrode (e.g., source electrode) in a down orientation or next to the printed circuit board, which lessens heat transfer capability. In other applications, this design places the main current carrying electrode in an up orientation or away from the printed circuit board, but in direct contact with an unpassivated heat sink, which is a safety concern under operation.
Accordingly, a need exists for semiconductor packages that have enhanced thermal dissipation characteristics without detrimentally impacting device reliability, safety, manufacturing cycle time, and cost.